This poster, presented by Chariton Christou at the 30th Scottish meeting on Fluid Mechanics in May 2017, describes the development of a new modelling approach to help understand the outgassing activity of comets. The new approach is based on modelling techniques used in the oil and gas exploration industry, and for this initial work uses porous terrestrial sandstones as analogue materials for a cometary surface (for this work the composition of the material is not important, just the porosity). Three-dimensional X-ray tomography images of the sandstones are used as inputs to the calculations.

This ‘3D rock file’ is the result of a CT scan (X-ray tomography) of a porous rock, by staff at Heriot-Watt University. On some platforms you can view and rotate it directly in your web-browser, otherwise it may be necessary to download it and use a viewer for .stl files. (‘Preview’ works on Macintosh computers).

Downloads

This section contains links to a number of datasets generated by the project. If you have questions about these datasets, or find bugs in the software to view the shape models, please email info@miard.eu

Virtual tour of museum exhibition ‘Comets – the Rosetta mission’

The MiARD project (principally partner DLR – the German Centre for Air and Space Research) developed a museum exhibition about the Rosetta mission and what we have learned from it. This exhibition was displayed in Berlin in 2016/ 2017 and (updated) is now at the Natural History Museum in Vienna until 12th September 2018. A virtual tour of the exhibition can be made at http://virtueller-rundgang-rosetta-ausstellung.dlr.de or by downloading the free apps from the Google Play store or Apple iTunes store.

High-resolution shape model of comet 67P/Churyumov-Gerasimenko

Pending archiving of the sub-meter accuracy SHAP7 space model (see Preusker et al 2017) in ESA and NASA repositories, it may be obtained on request from Frank.Preusker(at)dlr.de. Also available are files with OSIRIS NAC camera images draped as textures over the shape. See also http://europlanet.dlr.de/Rosetta/

The compressed file global_combined.zip (731 Mb) contains three versions of the high resolution shape model derived by combining the SPG and MSPCD approaches (article for Space & Planetary Science to be submitted in Q4/2018, in the meantime the methodology is described in the project’s deliverable report D1.1). The versions have either 12, 20 or 44 million facets.

The compressed files maplets_set1.zip (463 Mb) and maplets_set2.zip (420 Mb) contain between them 103 local digital terrain models (DTMs) or ‘maplets’ that were used in the generation of the global model.

the geometric parameters of the maplets (including number of facets, centre, surface and averaged sampling)

maplet coverage models

views of the coverage offered by the maplets

rendered images of the global models corresponding to images observed by the OSIRIS/NAC camera on Rosetta. Note also the availability of the SHAP 7 SPG model with camera images draped as textures over the shape model that is mentioned above.

Models are in the binary polygon file format (file extension .PLY) and images are in the Portable Network Graphic format (file extension .PNG).

VR viewer for the enhanced shape model of comet 67P

This VR Viewer for Windows for the enhanced shape model of comet 67P from the MiARD project uses a version of the high resolution model published by Preusker et al. ‘The global meter-level shape model of comet 67P/Churyumov-Gerasimenko‘, publication number 4 in the list above. To ease the computational burden, we used just 12 million facets, although the full model has 44 million facets. The viewer was built in Unity and can be used either with a normal PC screen, or in VR mode with an Oculus Rift headset.

To install the package, unzip the file linked above and save the resulting executable file along with the data folder in the same directory. Running the executable will start the viewer. If an Oculus Rift is connected, the viewer will automatically start in VR mode.

Local Digital Terrain Models (DTM or DEM)

For ten selected areas, fifteen specially prepared local models of the surface have been prepared by using the combined SPG/MSPCD approach developed within the MiARD project, see local DTM report. The datafile contains two directories:

extras contains images showing the location of each area on the comet, text files defining the orientation of the projections for the elevations (relative to the Cheops frame of reference for the comet), coloured maps for each DTM indicating the ‘quality’ of each DTM. the DEM’s in the binary FITS image format, and images highlighting any artefacts identified in each local DTM.

Viewer for local DTMs

The TerrainExplorer software for Windows computers, developed by the Laboratoire d’Astrophysique de Marseillse (CNRS) within the MiARD project, allows several selected DTMs from the project to be rendered and explored. It is important to read the Readme.txt file concerning the installaton before running the software.

Maps

The high resolution shape model from the project can be used to generate maps over the surface of a number of properties:

VIRTIS and MIRO ‘temperature’ maps

The origin of these VTK formatted data files is further explained in the MiARD D4.5 deliverable report “Mapping files of VIRTIS/MIRO data onto the 3D shape model”. These are rather large archives (1.6 Gb for the VIRTIS data, 0.8 Gb for the MIRO data). To view them, you will need software capable of opening VTK files (.vtu) such as Paraview.

Distribution in 3D of dust and gas

The MiARD project (in particular the University of Bern) has developed a numerical activity model for the outgassing and ejection of dust from the comet. The predictions of this model, for two sets of assumptions, are made available here. The data consists of 8 space separated ASCII files with seven columns of data. These seven columns (x, y, z, number density,u, v, w) are:

For each model (inhomogeneous or purely insolation driven) there is one file for the gas number density and velocity, and one file for each of the three dust particle sizes. The filenames should be self-explanatory. For more information, see the associated deliverable report.

Categories

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no 686709.

This work was supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 16.0008-2. The opinions expressed and arguments employed herein do not necessarily reflect the official view of the Swiss Government.